The present invention relates to a linerless label roll-up preventing device of a thermal printer and which particularly performs printing by loading a linerless label.
A strip-form label sheet is known which uses a linerless label to save resources. A wireless label does not use a liner (or peeling sheet) that is temporarily attached to an adhesive layer on the back surface of the label base member. Printers for such a linerless label have also been developed.
FIG. 4 is a schematic side-view of a thermal printer 1, which is an example of a conventional linerless label printer. The thermal printer 1 is, for example, configured to be portable. It has a printer housing 2, a label sheet holding and supplying unit 4 holding a linerless label sheet 3 in a roll, an internal transfer route 5, and a printing unit 6.
A belt 7 on the printer housing 2 makes the thermal printer 1 portable, to be carried for example, on the waist W of an operator.
The linerless label 3, as shown enlarged in FIG. 4a, has a strip-form label base member 8, an adhesive layer 9 formed on the back surface of the label base member 8, a lower layer thermal color forming agent layer 10 and an upper layer separating agent layer 11 formed on the surface of the label base member 8.
Therefore, if the linerless label sheet 3 is loaded in a roll form at the holding and supplying unit 4, since the separating agent layer 11 is contacting the adhesive agent layer 9, the inner layer side and the outer layer side of the roll will not adhere to each other, which enables feed out of the rolled linerless label 3 in a strip-form to the transfer route 5.
Furthermore, perforations (not shown in the diagram) at a predetermined pitch along the linerless label 3, enable cutting the printed linerless label 3 in a predetermined size.
The printing unit 6 has a thermal head 12 and an opposing platen roller 13. The printing unit 6 supplies the linerless label sheet 3 between the thermal head 12 and the platen roller 13, and transfers the linerless label sheet 3 by the rotating drive of the platen roller 13 such that it is possible to perform printing of a predetermined contents on the surface of the label base member 8.
Furthermore, the thermal head 12 is provided at the printer housing 2, and the platen roller 13 is provided rotatably at an end portion of an openable cover 15 around an opening-closing shaft 14 fixed on the printer housing 2.
The linerless label sheet 3 printed at the printing unit 6 is discharged outside of the printer housing 2 from the label outlet 16 of the printer housing 2, cut at the perforations of the label sheet, and attached to the predetermined portion.
In the thermal printer 1 having such a configuration, the parts of the transfer route 5 and the platen roller 13, etc., which contact the adhesive agent layer 9 at the back surface of the linerless label 3, are ensured of non-adhesiveness by themselves, by the use of necessary separable material or by being provided with surface preparation such that the surface has detachability (non-adhesiveness). For example, silicone rubber is used for the platen roller 13.
However, in prolonged use of the thermal printer 1 by its continuous use, the non-adhesiveness of the platen roller 13 will deteriorate, so the adhesive agent (adhesive paste) of the adhesive agent layer 9 gradually infiltrates into the platen roller 13, and furthermore, the adhesive agent adheres to the platen roller 13. Particularly as shown by the virtual line in the drawing, the printed linerless label sheet 3 is not transferring in the outlet 16 direction, but with the rotation of the platen roller 13, the printed linerless label 3 is adhering to the outer circumferential surface of the platen roller 13. This causes a problem in issuance and discharge of the linerless label 3 since the label is being rolled-up around the outer circumferential surface of the roller 13.